The present invention relates to a plastic frame for eyeglasses, comprising a center portion, temples and hinges for connecting the temples to the center portion, whereby the plastic frame has protruding parts in the form of nose cushions at the center portion and hinge supports for the hinges at the center portion and the temples. The plastic frame is manufactured by cutting or machining the frame, respectively, its center portion and/or its temples from a plastic blank.
The present invention is further concerned with a method for manufacturing such plastic frames for eyeglasses.
Plastic frames for eyeglasses of the aforementioned kind are commonly manufactured from a flat plastic blank, having dimensions of approximately 60 by 180 mm and a thickness of, for example, 10 mm, by respective milling or cutting processes or other machining steps and thus shaped to the desired form. For such a manufacturing process it is necessary to provide the flat plastic blank with a thickness of up to 12 mm, because for high-quality plastic frames a one-piece manufacturing of the center piece is required, and the plastic blank thus must have a respective thickness in the area of the nose cushions or nose pads.
The temples of the plastic frame are usually manufactured from plastic blank material having a considerably reduced thickness with respect to the plastic blanks for the center portions of, for example, 4 mm.
It is a disadvantage of the known methods that the plastic blanks of a great thickness, which, for example, consist of cellulose acetate, are comparably expensive. The cutting or milling process is relatively time consuming, and, furthermore, a great amount of discard material is produced. Also, time periods between deliveries for plastic blanks of various sizes and colors vary, thus requiring uneconomical storage of various plastic blanks in order to ensure a continuous manufacture according to the demands of the market.
For plastic frames which do not have to conform to extremely high quality standards, it is possible to glue thin plastic plates to the area of the nose cushions so that for manufacturing the center portions plastic blanks with a reduced thickness may be employed. However, the manufacturing process is even further prolonged because after the application of the thin plastic plates the blanks must be carefully dried for an extended period of time.
The drying time must be determined in practice. It depends also to a certain degree on the form and thickness of the frame to be manufactured, respectively, on the nose cushion portion. The drying time must be selected such that a complete drying is ensured. If the drying time is insufficient, depressions may be observed within the area of the gluing scam which result from the fact that the gluing surface areas, i.e. the surface areas of the blank and of the plastic plates which are facing one another and which are provided with the glue, have been partially dissolved during pretreatment before the gluing step. If such depressions occur, the plastic frame is practically unfit to be sold and must be discarded.
It is therefore an object of the present invention to provide a plastic frame for eyeglasses of the aforementioned kind as well as a respective manufacturing method which ensure a high product quality with economical manufacturing costs and reduces storage costs while providing a great color and shape selection of the plastic frame.